Two experiments on subtle mid-frequency hearing loss and its influence on word discrimination in noise-exposed listeners.

The present study consisted of two experiments. Experiment I was directed toward the detection of subtle mid-frequency cochlear dysfunction and the determination of word discrimination in noise for persons with noise-induced hearing loss. The presence of significantly elevated aural-overload thresholds, consistent with the presence of cochlear pathology in regions of normal pure-tone sensitivity, confirmed previous findings obtained with this subject population by other investigators. In addition, a marked reduction in word discrimination was observed in the presence of a background of competing noise. For experiment II, normal hearers listened to consonant-nucleus-consonant monosyllables filtered to match the mean audiometric configuration of the noise-exposed subjects in experiment I. Results showed significantly better performance with these filtered words by the normally hearing subjects than that by the noise-exposed group for unfiltered materials. The results of the second experiment were interpreted as providing further support for the presence of subtle auditory dysfunction in the mid-frequencies despite normal threshold sensitivity in this same frequency region.